城市绿化植物叶片表面特征对滞尘能力的影响

以西安市21种常见绿化植物为对象,采用人工降尘方法测定植物叶片的最大滞尘量,研究植物叶片表面绒毛、润湿性、表面自由能及其分量对滞尘能力的影响.结果表明： 21种供试植物叶片的最大滞尘量在0.8～38.6 g·m^-2,不同树种最大滞尘量差异显著,物种间相差40倍以上.叶片表面绒毛数量及其形态、分布特征对滞尘能力具有重要影响,可能与绒毛和颗粒物间的作用方式有关.除叶片表面着生绒毛的悬铃木、国槐、榆叶梅和毛梾4个物种外,其他植物叶片接触角与最大滞尘量均呈显著负相关.接触角较小、易润湿的植物叶片最大滞尘量在2.0～8.0 g·m^-2,而接触角较大的银杏、三叶草、紫叶小檗和鸡爪槭的最大滞尘量均＜2.0 g·m^-2.叶片表面自由能主要表现分子间色散力的作用,而极性分量对表面自由能的贡献低于20%,可能与叶片表面含有的非极性或弱极性物质有关.最大滞尘量与叶片表面自由能及其色散分量呈显著正相关,而与极性分量的相关关系不显著.

Relationships between leaf surface characteristics and dust-capturing capability of urban greening plant species

Taking 21 representative urban greening species in Xi’an as test objects, theirleaf dust-capturing capability was determined by artificial dust-deposition method, and the relationships between the dust-capturing capability and leaf surface features, e.g., trichomes, wettability, surface free energy and its polar and dispersive components on dust-capturing capability were studied. For the tested 21 species, their maximum leaf dust capturing capability was 0.8-38.6 g·m^-2, and there was a significant difference among them, with the greatest variation up to forty times. The amount, distribution, and morphology of trichomes had great influence on the leaf dust-capturing capability, possibly due to the different action patterns between trichomes and particulate matters. There was asignificant negative relationship between leaf contact angle and maximum leaf dust-capturing capability (r=-0.523), except for four species whose leaf surface has trichomes. For wettable leaves, their maximum dust-capturing capacityranged from 2.0 to 8.0 g·m^-2, but for nonwettable leaves, their maximumdust-capturing capacity was below 2.0 g·m^-2. The leaf surface free energy was mainly manifested in the action of dispersive component, while the contribution of polar free energy was lower than 20%, which could be related to the existence of non-polar or weakly polar substances on leaf surface. The leaf surface free energy and its dispersive component had a significant positive correlation (r=0.500, 0.572) with the maximum leaf dust-capturing capability, but the positive correlation between polar free energy and maximum dust-capturing capability was not significant (r=0.244).